I am installing a new wiring harness from Jim Carter on my 1946 two ton. About 4 inches below the headlight switch my truck has a small round push/pull switch that I believe is also a potentiometer - and is likely the 'instrument lamp rheostat switch.' The truck also has a 3 terminal slide switch mounted to the bottom edge of the dash on the passenger side of the steering wheel (the 'instrument lamp switch'). I have two wiring diagrams both of which picture the 3 terminal switch with the middle terminal connected to power at the headlight switch, the left terminal attached to instrument lights and the right terminal attached to the ignition lock light. There is no 'instrument rheostat switch' pictured on either diagram. The problem is that I have 2 wires only and they are labeled as connecting to the (apparently non-existent) instrument lamp rheostat switch even though they have large spade terminals identical to those on my existing instrument lamp switch and also cannot reach the location of the rheostat switch. Can someone please explain the operation of these switches and maybe give me a hint as to how to wire this. Thanks, PMH